Republican presidential hope Mitt Romney has described a requirement that all Americans buy health insurance as a "tax", seemingly backing away from a previous position that put him at odds with his party.

In an interview with CBS on Wednesday, Romney noted that the majority verdict in the supreme court was that the individual mandate, part of President Barack Obama's landmark healthcare reforms, is a tax.

"Therefore, it is a tax. They have spoken; there's no way around that," he added.

The comments contrast with that of his senior adviser Eric Fehrnstrom, who earlier indicated that the Republican presidential candidate believed the requirement to be a "penalty".

In an excerpt of the Romney interview released by CBS News, Romney also claimed that Obama broke his promise not to raise taxes on middle-class families by putting the mandate in place.

The semantic debate over whether the policy amounted to a "tax" or not had put Romney threatened a rift with many within his own party.

Last week, the supreme court, in a landmark 5-4 ruling, said that although not constitutional under the commerce clause of the constitution, the individual mandate was permissible as a tax.

Although the White House was delighted that the Affordable Care Act had been upheld, the decision was at odds with the administration's stated position that the policy of making citizens buy health cover or face a fine was a "penalty".

In an interview with MSNBC on Monday, Fehrnstrom said of Romney's position: "He disagreed with the ruling. He disagreed with the findings of the ruling. He disagreed with the logic that supported those findings. He said that he agreed with the dissent, which was written by Justice Scalia, and the dissent clearly stated that the mandate was not a tax."

Only a day earlier, Republican minority leader in the senate Mitch McConnell said the individual mandate was unequivocally a tax.

The debate over the terminology of the provision reflects the dilemma that healthcare reform poses for Romney. As governor of Massachusetts, Romney introduced a similar policy to Obama's.

Romney has repeatedly described it as a penalty, not a tax. Fehrnstrom reiterated this in his MSNBC interview. "The governor believes what we put in place in Massachusetts was a penalty, and he disagrees with the court's ruling that the mandate was a tax."